[1] It is a Norwegian/Danish/British co-production directed by Per-Olav Sørensen based on the true story of the German nuclear weapon project during the Second World War and the heavy water sabotage in Norway to disrupt it, with a particular emphasis on the role of the Norwegian intelligence officer Leif Tronstad.
[8][9] Viewing rights for France were bought by Entertainment One, for Benelux by Lumière, for Spain by A Contracorriente, for Poland by Kino Swiat and for the Balkans by Stas Media.
[11] Norwegian newspaper Verdens Gang gave the series a 5 out of 6, citing "It will enrage some historians, and some concerned will complain, but most television viewers will be engrossed".
[17] The same story was covered in the 1948 Franco-Norwegian film Kampen om tungtvannet (also known as La bataille de l'eau lourde or Operation Swallow: The Battle for Heavy Water).
Despite mainly sticking to the factual evidence, some scenes in the documentary were partly dramatised, focusing on the survival skills involved in the operation.